Methods of administering elagolix

ABSTRACT

The present disclosure relates to the use of GnRH receptor antagonists used in the treatment of endometriosis or uterine fibroids. In particular, the present disclosure describes a method of treating endometriosis or uterine fibroids, where the method involves the administration of elagolix, and where the method may further involve the co-administration of rifampin or ketoconazole.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/254,419, filed Sep. 1, 2016, which claims priority to U.S.Provisional Application No. 62/213,000, filed Sep. 1, 2015. The contentof each of the aforementioned applications is incorporated herein byreference in its entirety.

FIELD

The present disclosure pertains to the use of GnRH receptor antagonistsused in the treatment of endometriosis or uterine fibroids.

BACKGROUND

4-((R)-2-[5-(2-fluoro-3-methoxy-phenyl)-3-(2-fluoro-6-trifluoromethyl-benzyl)-4-methyl-2,6-dioxo-3,6-dihydro-2H-pyrimidin-1-yl]-1-phenyl-ethylamino)-butyricacid sodium salt (“Elagolix”) is a drug currently in development of thetreatment of the signs and symptoms of endometriosis and uterinefibroids.

Rifampin is an antibiotic used to treat bacterial infections. It is apotent CYP3A inducer and OATP inhibitor, and can typically lead todecreased exposure levels of many other drugs that are CYP enzymesubstrates when co-administered.

Ketoconazole is a synthetic imidazole drug that may be used, forexample, to treat fungal infections. It is a potent CYP3A and P-gpinhibitor.

SUMMARY

In embodiments, the present disclosure provides a method of treatingendometriosis, where the method involves the administration of elagolixat a dose of 150 mg once per day (“q.d.”), and further involves theco-administration of rifampin, after which the patient is treated at adose of less than 150 mg elagolix once per day.

In embodiments, the present disclosure provides a method of treatingendometriosis, where the method involves the administration of 150 mg ofelagolix once per day, and further involves the co-administration ofrifampin, after which the patient is treated with elagolix at a reduceddosing interval frequency of less than once per day.

In embodiments, the present disclosure provides a method of treatingendometriosis, where the method comprises administering 200 mg elagolixtwice daily (“b.i.d.”) and further comprises the co-administration ofrifampin, after which the patient is treated with elagolix b.i.d. at adose of less than 200 mg.

In embodiments, the present disclosure provides a method of treatingendometriosis, where the method involves the administration of 200 mgelagolix b.i.d. and further involves the co-administration of rifampinafter which the patient is treated with elagolix at a reduced dosinginterval frequency of less than twice per day.

In embodiments, the present disclosure provides a method of treating anendometriosis patient, where the method involves the b.i.d.administration of less than 200 mg elagolix and further comprises theco-administration of rifampin.

In embodiments, the present disclosure provides a method of treating anendometriosis patient, where the method involves the once dailyadministration of less than 150 mg elagolix and further comprises theco-administration of rifampin.

In embodiments, the present disclosure provides a method of treating apatient for uterine fibroids, where the method involves theadministration of elagolix at 300 mg b.i.d. and further involves theco-administration of rifampin, after which the patient is treated with areduced dosing interval of less than twice per day.

In embodiments, the present disclosure provides a method of treating anendometriosis patient, where the method involves the once dailyadministration of less than 150 mg elagolix and further involves theco-administration of rifampin.

In embodiments, the present disclosure provides a method for treating apatient for uterine fibroids, where the method involves theadministration of elagolix at 300 mg b.i.d. and further involves theco-administration of rifampin, after which the patient is treated with areduced dosing interval of less than twice per day.

In embodiments, the present disclosure provides a method of treating anendometriosis patient, where the method involves the administration ofelagolix according to a first dosing schedule. In embodiments, thepatient subsequently begins to take rifampin according to a rifampindosing schedule, and the patient adjust the first dosing schedule ofelagolix by reducing the amount of elagolix and/or by increasing theinterval between doses according to a second dosing schedule. Inembodiments, the second dosing schedule results in overall reducedelagolix exposure in the second dosing schedule relative to elagolixexposure in the first dosing schedule for a given time interval.

In embodiments, the present disclosure provides a method of treating apatient having uterine fibroids, where the method involves theadministration of elagolix according to a first dosing schedule. Inembodiments, the patent subsequently begins to take rifampin accordingto a rifampin dosing schedule, and the first dosing schedule of elagolixis adjusted by reducing the amount of elagolix and/or by increasing theinterval between doses according to a second dosing schedule. Inembodiments, the second dosing schedule results in in overall reducedelagolix exposure in the second dosing schedule relative to elagolixexposure in the first dosing schedule for a given time interval.

In embodiments, the present disclosure provides a method of treatingendometriosis, where the method involves the administration of elagolixat a dose of 150 mg once per day (“q.d.”), and further involves theco-administration of ketoconazole, after which the patient is treated ata dose of less than 150 mg elagolix once per day.

In embodiments, the present disclosure provides a method of treatingendometriosis, where the method involves the administration of 150 mg ofelagolix once per day, and further involves the co-administration ofketoconazole, after which the patient is treated with elagolix at areduced dosing interval frequency of less than once per day.

In embodiments, the present disclosure provides a method of treatingendometriosis, where the method comprises administering 200 mg elagolixtwice daily (“b.i.d.”) and further comprises the co-administration ofketoconazole, after which the patient is treated with elagolix b.i.d. ata dose of less than 200 mg.

In embodiments, the present disclosure provides a method of treatingendometriosis, where the method involves the administration of 200 mgelagolix b.i.d. and further involves the co-administration ofketoconazole after which the patient is treated with elagolix at areduced dosing interval frequency of less than twice per day.

In embodiments, the present disclosure provides a method of treating anendometriosis patient, where the method involves the b.i.d.administration of less than 200 mg elagolix and further comprises theco-administration of ketoconazole.

In embodiments, the present disclosure provides a method of treating anendometriosis patient, where the method involves the once dailyadministration of less than 150 mg elagolix and further comprises theco-administration of ketoconazole.

In embodiments, the present disclosure provides a method of treating apatient for uterine fibroids, where the method involves theadministration of elagolix at 300 mg b.i.d. and further involves theco-administration of ketoconazole, after which the patient is treatedwith a reduced dosing interval of less than twice per day.

In embodiments, the present disclosure provides a method of treating anendometriosis patient, where the method involves the once dailyadministration of less than 150 mg elagolix and further involves theco-administration of ketoconazole.

In embodiments, the present disclosure provides a method for treating apatient for uterine fibroids, where the method involves theadministration of elagolix at 300 mg b.i.d. and further involves theco-administration of ketoconazole, after which the patient is treatedwith a reduced dosing interval of less than twice per day.

In embodiments, the present disclosure provides a method of treating anendometriosis patient, where the method involves the administration ofelagolix according to a first dosing schedule. In embodiments, thepatient subsequently begins to take ketoconazole according to aketoconazole dosing schedule, and the patient adjust the first dosingschedule of elagolix by reducing the amount of elagolix and/or byincreasing the interval between doses according to a second dosingschedule. In embodiments, the second dosing schedule results in overallreduced elagolix exposure in the second dosing schedule relative toelagolix exposure in the first dosing schedule for a given timeinterval.

In embodiments, the present disclosure provides a method of treating apatient having uterine fibroids, where the method involves theadministration of elagolix according to a first dosing schedule. Inembodiments, the patent subsequently begins to take ketoconazoleaccording to a ketoconazole dosing schedule, and the first dosingschedule of elagolix is adjusted by reducing the amount of elagolixand/or by increasing the interval between doses according to a seconddosing schedule. In embodiments, the second dosing schedule results inoverall reduced elagolix exposure in the second dosing schedule relativeto elagolix exposure in the first dosing schedule for a given timeinterval.

DESCRIPTION OF THE DRAWINGS

FIG. 1 shows Mean+SD Elagolix plasma concentration-time profiles forelagolix administered with single and multiple doses of rifampin, versuselagolix administered alone.

FIG. 2 shows mean elagolix plasma concentration-time profiles forelagolix administered with ketoconazole, versus elagolix administeredalone.

DETAILED DESCRIPTION

Elagolix is a small molecule antagonist of the GNRH receptor and itsadministration results in decreased levels of luteinizing hormone (“LH”)and follicle stimulating hormone (“FSH”) with corresponding suppressionof the primary sex steroid hormones. Elagolix has shown significanteffects in ameliorating many of the symptoms of endometriosis anduterine fibroids. The drug is currently being evaluated at 150 mg q.d.and 200 mg b.i.d. for endometriosis and 300 mg b.i.d. for fibroids.

During the course of drug-drug interaction studies, surprisingly it wasdiscovered that rifampin significantly increased elagolix concentrationsboth acutely (after a single dose) and chronically after several doses.This discovery allows the possibility of reducing normal elagolix doseswithout compromising efficacy. In particular, it has been discoveredthat rifampin significantly increases elagolix exposures when the drugsare co-administered (present in the body at the same time). This resultis surprising since rifampin is a known Cyp enzyme up-regulator andtypically can lead to decreased exposure levels of many other drugs whenco-administered. This discovery has the potential to modify accepteddosage regimens by decreasing the daily dosage and/or increasing thedosing interval (i.e., increasing the time between dosages). It has alsobeen found that ketoconazole has the effect of increasing drug exposurelevels and co-administration of elagolix with ketoconazole can alsoallow for a drug down-titration vis-à-vis dose or dosing intervaladjustments.

In some embodiments of this invention, a revised elagolix dosing schemeis described wherein the dose of elagolix is down-titrated whenadministered with rifampin from the typical elagolix dose which is 150mg q.d. or 200 mg b.i.d. for endometriosis. For example, the 150 mg dosecould be reduced to 125 mg, 100 mg, 75 mg, 50 mg or integer multiplesbetween. In embodiments, a revised elagolix dosing scheme is providedwhere the time between doses is increased, including for example, thepossibility of going from a q.d. elagolix schedule to an every other dayschedule or from a b.i.d. schedule to a q.d. schedule.

In embodiments, a revised elagolix dosing scheme is described whereinthe dose of elagolix is down-titrated when co-administered with rifampinfrom the typical dose which is 300 mg b.i.d. for uterine fibroids. Forexample, the 300 mg dose could be reduced to 250 mg, 200 mg, 150 mg, 100mg or integer multiples between. In embodiments, a revised elagolixdosing scheme is provided where the dosing interval is increased betweendosing, including for example, the possibility of going from a b.i.d.schedule to a q.d. schedule.

In the broader sense, it is important to consider that the dosingschedules that are adjusted can be done for a period of time but do nothave to stay fixed at their adjusted level. Nor do they need to bereduced to a fixed schedule. Many of those specifically enumeratedherein which are provided for by way of just some examples. Thephysician or patient has the option of reducing to any lower dose and/orincreasing the period between doses for as long as needed, after whichtime they can adjust to a new reduced dose schedule or revert back totheir original dose schedule. This provides maximum flexibility for thepatient and/or physician to titrate the drug to his or her individualneed and at their discretion.

In embodiments, the dosage regimen may modified by decreasing the dailydosage. For example, in embodiments, the present disclosure provides amethod of treating endometriosis, where the method involves theadministration of elagolix at a dose of 150 mg once per day. Inembodiments, the method further involves the co-administration ofrifampin, after which the patient is treated at a dose of less than 150mg elagolix once per day.

In embodiments, the present disclosure provides a method of treatingendometriosis, where the method involves the administration of 200 mgelagolix twice daily (b.i.d.). In embodiments, the method furtherinvolves the co-administration of rifampin, after which the patient istreated with elagolix b.i.d. at a dose of less than 200 mg.

In embodiments, the dosage regimen may be modified by increasing thedosing interval (i.e., increasing the time between dosages). Forexample, in embodiments, the present disclosure provides a method oftreating endometriosis, where the method involves the administration of150 mg elagolix once per day. In embodiments, the method furthercomprises the co-administration of rifampin, after which the patient istreated with elagolix at a reduced dosing interval frequency of lessthan once per day. In embodiments, the reduced dosing interval frequencymay be once per every other day.

In embodiments, the present disclosure provides a method of treatingendometriosis, where the method involves the administration of 20 mgelagolix b.i.d. In embodiments, the method further comprises theco-administration of rifampin, after which the patient is treated withelagolix at a reduced dosing interval frequency of less than twice perday. For example, in embodiments, the reduced dosing interval is onceper day. In embodiments, the method further involves the administrationof an estrogen and a progestin. In embodiments, the estrogen is17β-estradiol and said progestin is norethindrone acetate.

In embodiments, the present disclosure provides a method of treating anendometriosis patient, where the method involves the b.i.d.administration of less than 200 mg elagolix and further comprises theco-administration of rifampin.

In embodiments, the present disclosure provides a method of treating anendometriosis patient, where the method involves the once dailyadministration of less than 150 mg elagolix, and further involves theco-administration of rifampin.

In embodiments, the present disclosure provides a method of treatinguterine fibroids, where the method involves the administration ofelagolix at 300 mg b.i.d. and further comprises the co-administration ofrifampin, after which the patient is treated with a reduced dosinginterval of less than twice per day. In embodiments, the reduced dosinginterval is once per day. In embodiments, the patient is further treatedwith an estrogen and a progestin. In embodiments, the estrogen is17β-estradiol and said progestin is norethindrone acetate.

In embodiments, the administration is per the oral route.

In embodiments, in the methods described in the present disclosure,rifampin is given as 600 mg twice per day. In embodiments, in themethods described in the present disclosure, rifampin is given at a doseof about 10 mg/kg per day.

In embodiments, the present disclosure provides a method of treatingendometriosis, where the method involves the administration of elagolixaccording to a first dosing schedule. The patient subsequently begins totake rifampin according to a rifampin dosing schedule. After the patientbegins to take rifampin according to the rifampin dosing schedule, thefirst dosing schedule of elagolix is adjusted. In embodiments, the firstdosing schedule is reduced by reducing the amount of elagolix and/or byincreasing the interval between doses according to a second dosingschedule. In embodiments, the second dosing schedule results in overallreduced elagolix exposure in the second dosing schedule relative toelagolix exposure in the first dosing schedule for a given timeinterval.

In embodiments, in the first dosing schedule, elagolix is administeredat 150 mg once per day, and in the second dosing schedule, elagolix isadministered at less than 150 mg per day, and/or elagolix isadministered once every other day or less.

In embodiments, the first dosing schedule involves administeringelagolix at 200 mg b.i.d., and the second dosing schedule involves theadministration of less than 200 mg per dose and/or dosing less thantwice per day. For example, in the second dosing schedule, with respectto dosing less than twice per day, in embodiments elagolix isadministered once per day.

In embodiments, the present disclosure provides a method of treating apatient having uterine fibroids, where the method involves theadministration of elagolix according to a first dosing schedule. Inembodiments, the patient subsequently begins to take rifampin accordingto a rifampin dosing schedule, and the first dosing schedule of elagolixis adjusted by reducing the amount of elagolix per dose and/or byincreasing the interval between doses according to a second dosingschedule. In embodiments, the second dosing schedule results in overallreduced elagolix exposure in the second dosing schedule relative toelagolix exposure in the first dosing schedule for a given time period.In embodiments, according to the first dosing schedule, elagolix isadministered at 300 m.g. b.i.d., and according to the second dosingschedule, elagolix is administered at less than 300 mg per dose, and/orelagolix is administered less than twice per day. For example, withrespect to administering elagolix less than twice per day in the seconddosing schedule, in embodiments, elagolix is administered once per day.In embodiments, the method further comprises administering an estrogenand a progestin. In embodiments, the estrogen is 17β-estradiol and saidprogestin is noerthindrone acetate.

In embodiments, all of the drugs may be taken orally.

As discussed above, it was further determined that ketoconazole has theeffect of increasing drug exposure levels. Accordingly,co-administration of elagolix with ketoconazole can also allow for adrug down-titration with respect to dose or dosing interval adjustments.

In embodiments, a revised elagolix dosing scheme is described whereinthe dose of elagolix is down-titrated when administered withketoconazole from the typical elagolix dose which is 150 mg q.d. or 200mg b.i.d. for endometriosis. For example, the 150 mg dose could bereduced to 125 mg, 100 mg, 75 mg, 50 mg or integer multiples between. Incertain embodiments of this invention a revised elagolix dosing schemeis provided where the time between doses is increased, including forexample, the possibility of going from a q.d. elagolix schedule to anevery other day schedule or from a b.i.d. schedule to a q.d. schedule.

In some embodiments of this invention, a revised elagolix dosing schemeis described wherein the dose of elagolix is down-titrated whenco-administered with ketoconazole from the typical dose which is 300 mgb.i.d. for uterine fibroids. For example, the 300 mg dose could bereduced to 250 mg, 200 mg, 150 mg, 100 mg or integer multiples between.In certain embodiments of this invention a revised elagolix dosingscheme is provided where the dosing interval is increased betweendosing, including for example, the possibility of going from a b.i.d.schedule to a q.d. schedule.

In embodiments, the dosage regimen may modified by decreasing the dailydosage. For example, in embodiments, the present disclosure provides amethod of treating endometriosis, where the method involves theadministration of elagolix at a dose of 150 mg once per day. Inembodiments, the method further involves the co-administration ofketoconazole, after which the patient is treated at a dose of less than150 mg elagolix once per day.

In embodiments, the present disclosure provides a method of treatingendometriosis, where the method involves the administration of 200 mgelagolix twice daily (b.i.d.). In embodiments, the method furtherinvolves the co-administration of ketoconazole, after which the patientis treated with elagolix b.i.d. at a dose of less than 200 mg.

In embodiments, the dosage regimen may be modified by increasing thedosing interval (i.e., increasing the time between dosages). Forexample, in embodiments, the present disclosure provides a method oftreating endometriosis, where the method involves the administration of150 mg elagolix once per day. In embodiments, the method furthercomprises the co-administration of ketoconazole, after which the patientis treated with elagolix at a reduced dosing interval frequency of lessthan once per day. In embodiments, the reduced dosing interval frequencymay be once per every other day.

In embodiments, the present disclosure provides a method of treatingendometriosis, where the method involves the administration of 20 mgelagolix b.i.d. In embodiments, the method further comprises theco-administration of ketoconazole, after which the patient is treatedwith elagolix at a reduced dosing interval frequency of less than twiceper day. For example, in embodiments, the reduced dosing interval isonce per day. In embodiments, the method further involves theadministration of an estrogen and a progestin. In embodiments, theestrogen is 17β-estradiol and said progestin is norethindrone acetate.

In embodiments, the present disclosure provides a method of treating anendometriosis patient, where the method involves the b.i.d.administration of less than 200 mg elagolix and further comprises theco-administration of ketoconazole.

In embodiments, the present disclosure provides a method of treating anendometriosis patient, where the method involves the once dailyadministration of less than 150 mg elagolix, and further involves theco-administration of ketoconazole.

In embodiments, the present disclosure provides a method of treatinguterine fibroids, where the method involves the administration ofelagolix at 300 mg b.i.d. and further comprises the co-administration ofketoconazole, after which the patient is treated with a reduced dosinginterval of less than twice per day. In embodiments, the reduced dosinginterval is once per day. In embodiments, the patient is further treatedwith an estrogen and a progestin. In embodiments, the estrogen is17β-estradiol and said progestin is norethindrone acetate.

In embodiments, the administration is per the oral route.

In embodiments, the present disclosure provides a method of treatingendometriosis, where the method involves the administration of elagolixaccording to a first dosing schedule. The patient subsequently begins totake ketoconazole according to a ketoconazole dosing schedule. After thepatient begins to take ketoconazole according to the ketoconazole dosingschedule, the first dosing schedule of elagolix is adjusted. Inembodiments, the first dosing schedule is reduced by reducing the amountof elagolix and/or by increasing the interval between doses according toa second dosing schedule. In embodiments, the second dosing scheduleresults in overall reduced elagolix exposure in the second dosingschedule relative to elagolix exposure in the first dosing schedule fora given time interval.

In embodiments, in the first dosing schedule, elagolix is administeredat 150 mg once per day, and in the second dosing schedule, elagolix isadministered at less than 150 mg per day, and/or elagolix isadministered once every other day or less.

In embodiments, the first dosing schedule involves administeringelagolix at 200 mg b.i.d., and the second dosing schedule involves theadministration of less than 200 mg per dose and/or dosing less thantwice per day. For example, in the second dosing schedule, with respectto dosing less than twice per day, in embodiments elagolix isadministered once per day.

In embodiments, the present disclosure provides a method of treating apatient having uterine fibroids, where the method involves theadministration of elagolix according to a first dosing schedule. Inembodiments, the patient subsequently begins to take ketoconazoleaccording to a ketoconazole dosing schedule, and the first dosingschedule of elagolix is adjusted by reducing the amount of elagolix perdose and/or by increasing the interval between doses according to asecond dosing schedule. In embodiments, the second dosing scheduleresults in overall reduced elagolix exposure in the second dosingschedule relative to elagolix exposure in the first dosing schedule fora given time period. In embodiments, according to the first dosingschedule, elagolix is administered at 300 m.g. b.i.d., and according tothe second dosing schedule, elagolix is administered at less than 300 mgper dose, and/or elagolix is administered less than twice per day. Forexample, with respect to administering elagolix less than twice per dayin the second dosing schedule, in embodiments, elagolix is administeredonce per day. In embodiments, the method further comprises administeringan estrogen and a progestin. In embodiments, the estrogen is17β-estradiol and said progestin is noerthindrone acetate.

In embodiments, all of the drugs may be taken orally.

The term “co-administered” means, for instance, the drugs can be takentogether or sequentially.

Certain aspects of the disclosure are described in greater detail in thenon-limiting Examples that follow:

Example 1

This study was designed to assess the pharmacokinetic interactionbetween elagolix and rifampin (a potent CYP3A inducer and OATPinhibitor) and the safety in healthy premenopausal females. This was anopen-label, two-period, sequential study conducted in 12 females chosenaccording to the protocol selection criteria. Each subject receivedelagolix 150 mg single dose with and without rifampin 600 mg q.d. for 10days. Intensive blood samples for elagolix assay were collected up to 36hours after elagolix dosing in both periods. Safety data, includingadverse event monitoring, vital signs, ECGs, and laboratory tests werecollected during the study.

Values for elagolix maximum concentration (C_(max)) andarea-under-the-curve (AUC) were estimated using noncompartmentalmethods. Analysis of variance was performed to compare elagolix C_(max)and AUC with and without rifampin. Elagolix C_(max) and AUC increased by4.4 and 5.6 fold, when co-administered with a single rifampin dose, andincreased by 2.0 and 1.65 fold after multiple rifampin doses,respectively. Adverse event rates across treatment periods were 41.7%(elagolix alone), 83.3% (rifampin alone), and up to 50.0%(co-administration). The most common adverse events were GI-related,occurring most frequently with rifampin alone. No clinically significantvital signs, ECG or laboratory measurements were observed during thestudy. Inhibition of OATP by rifampin increases elagolix concentrationseven after accounting for rifampin's inductive effects after multipledosing. There were no new or unknown safety findings in this study. Meanand SD Elagolix plasma concentration-time profiles for elagolixadministered with single and multiple doses of rifampin, versus elagolixadministered alone, are shown in FIG. 1.

Example 2

In a second embodiment of this invention, it was discovered thatketoconazole increased elagolix exposure levels. This study was designedto assess the pharmacokinetic interaction between elagolix andketoconazole (a potent CYP3A and P-gp inhibitor) and the safety inhealthy premenopausal females.

This was an open-label, two-period, sequential study conducted in 12healthy premenopausal females chosen according to the protocol selectioncriteria. Each subject received elagolix 150 mg single dose alone and onthe 4^(th) day of a six-day regimen of ketoconazole 400 mg q.d.

Intensive blood samples for elagolix assay were collected up to 72 hoursafter elagolix dosing in both periods. Safety data, including adverseevent monitoring, vital signs, ECGs, and laboratory tests were collectedduring the study.

Values for elagolix maximum concentrations (C_(max)) andarea-under-the-curve (AUC) were estimated using noncompartmentalmethods. Analysis of variance was performed to compare thepharmacokinetic parameters of elagolix with and without ketoconazole.

When coadministered with ketoconazole, elagolix C_(max) and AUC valuesincreased 1.8- and 2.2-fold, respectively, relative to administration ofelagolix alone. Adverse event rates across treatment periods were 0%(elagolix alone), 82% (ketoconazole alone), and 36% (co-administration).The most common adverse event was nausea, which was noted as probablyrelated to ketoconazole alone. No clinically significant vital signs,ECG or laboratory measurements were observed during the study. Meanelagolix plasma concentration-time profiles for elagolix administeredwith ketoconazole, versus elagolix administered alone, are shown in FIG.2.

It is to be understood that the foregoing detailed description andaccompanying examples are merely illustrative and are not to be taken aslimitations upon the scope of the disclosure, which is defined by theappended claims and their examples.

The invention claimed is:
 1. A method for treating endometriosis in apatient, the method comprising: orally administering to the patient oncedaily4-((R)-2-[5-(2-fluoro-3-methoxy-phenyl)-3-(2-fluoro-6-trifluoromethyl-benzyl)-4-methyl-2,6-dioxo-3,6-dihydro-2H-pyrimidin-1-yl]-1-phenyl-ethylamino)-butyric acid as a sodium salt (elagolix), wherein the sodiumsalt is administered in an amount equivalent to 150 mg of the free acid;wherein the patient receives a single dose of 600 mg of rifampin,wherein maximum plasma concentration for elagolix is increased by 4.4fold relative to administration of elagolix alone and wherein plasmaarea-under-the-curve for elagolix is increased by 5.6 fold relative toadministration of elagolix alone.
 2. A method for treating endometriosisin a patient, the method comprising: orally administering to the patientonce daily4-((R)-2[5-(2-fluoro-3-methoxy-phenyl)-3-(2-fluoro-6-trifluoromethyl-benzyl)-4-methyl-2,6-dioxo-3,6-dihydro-2H-pyrimidin-1-yl]-1-phenyl-ethylamino)-butyric acid as a sodium salt (elagolix), wherein the sodiumsalt is administered in an amount equivalent to 150 mg of the free acid;wherein the patient receives 600 mg of rifampin once daily, whereinmaximum plasma concentration for elagolix is increased by 2.0 foldrelative to administration of elagolix alone and wherein plasmaarea-under-the-curve for elagolix is increased by 1.65 fold relative toadministration of elagolix alone.